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Hubert Chanson - One of the best experts on this subject based on the ideXlab platform.
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Aeration and air–water mass transfer on stepped chutes with Embankment Dam slopes
Environmental Fluid Mechanics, 2015Co-Authors: Stefan Felder, Hubert ChansonAbstract:Stepped spillway flows are characterised by significant free-surface aeration downstream of the inception point of air entrainment. The stepped design is advantageous for applications which require large energy dissipation and strong flow aeration. While the energy dissipation rate for Embankment stepped spillways was studied previously, the optimum design for aeration and air–water mass transfer is not known. Herein new air–water flow experiments were conducted on several stepped spillways with Embankment Dam slopes using with phase-detection intrusive probes. The present data were compared with previous studies in terms of energy dissipation, flow aeration and air–water mass transfer. The air–water mass transfer was calculated based upon air–water flow measurements in terms of dissolved oxygen. The re-oxygenation rates were compared with previous studies comprising both conductivity and direct dissolved oxygen measurements. The comparison highlighted a monotonic increase of aeration efficiency with energy dissipation rate. All data were in good agreement independent of channel slopes, stepped configuration and sensor size. The data confirmed the effects of strong air–water interactions within the bulk of the flow for both energy dissipation and re-oxygenation performances.
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aeration and air water mass transfer on stepped chutes with Embankment Dam slopes
Environmental Fluid Mechanics, 2015Co-Authors: Stefan Felder, Hubert ChansonAbstract:Stepped spillway flows are characterised by significant free-surface aeration downstream of the inception point of air entrainment. The stepped design is advantageous for applications which require large energy dissipation and strong flow aeration. While the energy dissipation rate for Embankment stepped spillways was studied previously, the optimum design for aeration and air–water mass transfer is not known. Herein new air–water flow experiments were conducted on several stepped spillways with Embankment Dam slopes using with phase-detection intrusive probes. The present data were compared with previous studies in terms of energy dissipation, flow aeration and air–water mass transfer. The air–water mass transfer was calculated based upon air–water flow measurements in terms of dissolved oxygen. The re-oxygenation rates were compared with previous studies comprising both conductivity and direct dissolved oxygen measurements. The comparison highlighted a monotonic increase of aeration efficiency with energy dissipation rate. All data were in good agreement independent of channel slopes, stepped configuration and sensor size. The data confirmed the effects of strong air–water interactions within the bulk of the flow for both energy dissipation and re-oxygenation performances.
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Embankment Dam spillways and energy dissipators
2014Co-Authors: Hubert ChansonAbstract:For the last fifty years, the design floods of a number of Embankment Dams were re-evaluated and the revised spillway outflows are often larger than the original design discharges. Several Embankment overtopping protection systems were developed for earthfill structures, and the applications range from river dykes to tsunami protections including Embankment Dams. Well- known designs include timber cribs, sheet-piles, riprap and gabions, reinforced earth, minimum energy loss (MEL) weirs, Embankment overflow stepped spillways and the precast concrete block protection systems. In this review, several design techniques are reviewed and discussed based upon prototype experiences. A critical analysis of their performances highlights that a safe operation of Embankment Dam spillways and associated energy dissipators relies upon a sound design and a good quality of construction, suitable flow conditions, together with regular maintenance
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energy dissipation and residual energy on Embankment Dam stepped spillways
33rd IAHR Biennial Congress, 2009Co-Authors: Stefan Felder, Hubert ChansonAbstract:Stepped spillways are designed to increase the rate of energy dissipation on the chute and to reduce the size of the downstream energy dissipator. It is essential to predict accurately the turbulent dissipation above the steps for large discharges per unit width corresponding to the skimming flow regime. New measurements were conducted in a large facility with a channel slope of 21.8o and a step height of 0.05 m. The experiments were performed with dimensionless discharges dc/h between 1.17 and 3.16, and flow Reynolds numbers up to 7.2E+5. The waters were highly turbulent and they dissipated a major proportion of the flow kinetic energy. Taking into account the free-surface aeration, the present results showed a decreasing rate of energy dissipation on the steps with increasing discharge: from about 80% for small discharges to less than 60% for medium to large flow rates. The residual energy data were compared with earlier studies conducted with step heights from 0.025 to 0.143 m, and invert slope between 3.4 and 26.6°. The results implied that the dimensionless residual head was about 2.7 < Hres/dc < 3.1 with a median value of 3.0 for a slope = 21.8 and 26.6°, and between 3.7 < Hres/dc < 5 with a median value of 4.5 for a slope = 3.4 and 15.9° independently of the step height and discharge. Altogether the comparative analysis yields some simple and basic design guidelines for Embankment Dam stepped spillways.
Michael Oberguggenberger - One of the best experts on this subject based on the ideXlab platform.
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assessment of long term coordinate time series using hydrostatic season time model for rock fill Embankment Dam
Structural Control & Health Monitoring, 2017Co-Authors: Sonja Gamse, Michael OberguggenbergerAbstract:Summary The safety control of Dams is based on monitoring activities and modelling of registered observations. The statistical hydrostatic-season-time model was originally developed and proposed for analyzing of monitoring data on concrete Dams. In some later works, the model was implemented for earth-fill Embankment Dams. The model admits a simultaneous estimation of hydrostatic load, temperature influences and irreversible deformations. In our study, we analyze long-term coordinate time series of a geodetic point on the crest of a rock-fill Embankment Dam. Coordinate time series are result of an adjustment of the observations in a permanent geodetic network for different epochs. An optimal model is defined using a multiple linear regression by combined process of exclusion and inclusion of individual parameters. In the process, different statistical parameters are observed. The analyses confirmed that not all parameters are significant. The most interesting and important conclusion of computations can be stated as follows: after inclusion of significant coefficients of the hydrostatic load and long-term trend, the residual time series still expose underlying periodicities. They can be removed by inclusion of at least one parameter of the seasonal term, where the temperature influences (i.e. air, water and soil) are modelled. The influences of the temperature on the Dam are not significant in any direction, but the inclusion of the parameters improves the statistical performance of the used model. Copyright © 2016 John Wiley & Sons, Ltd.
Sima Samadi - One of the best experts on this subject based on the ideXlab platform.
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Effect of Inclined Clay Core on Embankment Dam Seepage and Stability Through LEM and FEM
Geotechnical and Geological Engineering, 2020Co-Authors: Farzin Salmasi, Reza Norouzi, John Abraham, Bahram Nourani, Sima SamadiAbstract:Water seepage affects Dam stability and loss of water from reservoirs. Consequently, seepage is an important problem in the design, implementation, and operation of Embankment Dams. One type of Embankment Dam is a non-homogeneous (zoned) Dam with a clay core. Water passes through the core of the Dam and loses much of its energy due to friction. Zoned Embankment Dams can be designed and implemented with inclined or vertical cores. In this study, the performance of inclined and vertical cores are compared using numerical models to simulate the seepage and hydraulic gradients. Also, the Limit of Equilibrium Method is used to calculate slope stability. The permeability ratio of the Dam shell to the clay core is a variable. The result of this study shows that seepage with a vertical core is less than that with an inclined core. Meanwhile, the factor of safety for upstream slope failure is higher (about 55.5%) for the Embankment with an inclined core compared to the vertical core case. Also, comparisons were made using different methods to calculate the stability of the slope. The Bishop’s method showed the highest safety factor and the Fellenius’ method predicts the lowest safety factor.
Zongliang Zhang - One of the best experts on this subject based on the ideXlab platform.
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large scale in situ test for mechanical characterization of soil rock mixture used in an Embankment Dam
International Journal of Rock Mechanics and Mining Sciences, 2016Co-Authors: Zongliang Zhang, Wei Xia, Haiyang ZhangAbstract:Abstract To improve the mechanical behavior of core wall in higher Embankment Dams, soil–rock mixture obtained by mixing rock blocks to the cohesive soil is used for the first time as the core wall material of the Nuozhadu Embankment Dam, China. The differences in the mechanical behavior of soil and soil–rock mixture samples are studied in depth. Two large-scale compaction test fields and a series of in-situ direct shear tests have been conducted on soil and soil–rock mixture samples. The mixing of rock blocks changes the deformation behavior of the sample. The existence of rock blocks makes the deformation modulus and the internal friction angle of soil–rock mixture greater than that of the soil sample, while decreasing its cohesive force.
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discrete element modelling of a soil rock mixture used in an Embankment Dam
International Journal of Rock Mechanics and Mining Sciences, 2016Co-Authors: Shi Wang, Haiyang Zhang, Zongliang ZhangAbstract:Abstract The deformation and failure mechanism and the mechanical behavior of soil and soil-rock mixture used in an Embankment Dam was studied using numerical testing, based on a discrete element method (DEM). In this work, a 3D random meso-structure modelling system of soil-rock mixture is developed and used to generate a meso-structural model of soil-rock mixture. A non-overlapping combination method was used to model convex polyhedron rock blocks for the DEM numerical simulation. Based on the Voronoi cell, a method representing volume strain at particle scale is proposed. Results show that there is close contact between macro mechanical behavior and deformation localization of the sample. Rotation, occlusion, dilatation and a self-organizing force chains are remarkable phenomena of the localization band, and occur simultaneously with localization. Rock blocks influence localization characteristics and distribution of the force chains of the soil-rock mixture sample. Rotation and overcoming of the occlusion of the larger rock blocks in the localization band are more difficult than for small soil particles, which is the important reason for higher shear strength of soil-rock mixture than that of soil. The shearing process leads to anisotropy of the contact force, reaching its maximum at the start point of the plastic deformation, and then begins to decrease in the subsequent process.
Stefan Felder - One of the best experts on this subject based on the ideXlab platform.
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aeration and air water mass transfer on stepped chutes with Embankment Dam slopes
Environmental Fluid Mechanics, 2015Co-Authors: Stefan Felder, Hubert ChansonAbstract:Stepped spillway flows are characterised by significant free-surface aeration downstream of the inception point of air entrainment. The stepped design is advantageous for applications which require large energy dissipation and strong flow aeration. While the energy dissipation rate for Embankment stepped spillways was studied previously, the optimum design for aeration and air–water mass transfer is not known. Herein new air–water flow experiments were conducted on several stepped spillways with Embankment Dam slopes using with phase-detection intrusive probes. The present data were compared with previous studies in terms of energy dissipation, flow aeration and air–water mass transfer. The air–water mass transfer was calculated based upon air–water flow measurements in terms of dissolved oxygen. The re-oxygenation rates were compared with previous studies comprising both conductivity and direct dissolved oxygen measurements. The comparison highlighted a monotonic increase of aeration efficiency with energy dissipation rate. All data were in good agreement independent of channel slopes, stepped configuration and sensor size. The data confirmed the effects of strong air–water interactions within the bulk of the flow for both energy dissipation and re-oxygenation performances.
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Aeration and air–water mass transfer on stepped chutes with Embankment Dam slopes
Environmental Fluid Mechanics, 2015Co-Authors: Stefan Felder, Hubert ChansonAbstract:Stepped spillway flows are characterised by significant free-surface aeration downstream of the inception point of air entrainment. The stepped design is advantageous for applications which require large energy dissipation and strong flow aeration. While the energy dissipation rate for Embankment stepped spillways was studied previously, the optimum design for aeration and air–water mass transfer is not known. Herein new air–water flow experiments were conducted on several stepped spillways with Embankment Dam slopes using with phase-detection intrusive probes. The present data were compared with previous studies in terms of energy dissipation, flow aeration and air–water mass transfer. The air–water mass transfer was calculated based upon air–water flow measurements in terms of dissolved oxygen. The re-oxygenation rates were compared with previous studies comprising both conductivity and direct dissolved oxygen measurements. The comparison highlighted a monotonic increase of aeration efficiency with energy dissipation rate. All data were in good agreement independent of channel slopes, stepped configuration and sensor size. The data confirmed the effects of strong air–water interactions within the bulk of the flow for both energy dissipation and re-oxygenation performances.
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energy dissipation and residual energy on Embankment Dam stepped spillways
33rd IAHR Biennial Congress, 2009Co-Authors: Stefan Felder, Hubert ChansonAbstract:Stepped spillways are designed to increase the rate of energy dissipation on the chute and to reduce the size of the downstream energy dissipator. It is essential to predict accurately the turbulent dissipation above the steps for large discharges per unit width corresponding to the skimming flow regime. New measurements were conducted in a large facility with a channel slope of 21.8o and a step height of 0.05 m. The experiments were performed with dimensionless discharges dc/h between 1.17 and 3.16, and flow Reynolds numbers up to 7.2E+5. The waters were highly turbulent and they dissipated a major proportion of the flow kinetic energy. Taking into account the free-surface aeration, the present results showed a decreasing rate of energy dissipation on the steps with increasing discharge: from about 80% for small discharges to less than 60% for medium to large flow rates. The residual energy data were compared with earlier studies conducted with step heights from 0.025 to 0.143 m, and invert slope between 3.4 and 26.6°. The results implied that the dimensionless residual head was about 2.7 < Hres/dc < 3.1 with a median value of 3.0 for a slope = 21.8 and 26.6°, and between 3.7 < Hres/dc < 5 with a median value of 4.5 for a slope = 3.4 and 15.9° independently of the step height and discharge. Altogether the comparative analysis yields some simple and basic design guidelines for Embankment Dam stepped spillways.